I'm not sure how much help you are looking for specifically. You could do this using native libraries or RhoMobile. As a LAN connection is likely over TCP, the easiest thing to remember is the IP address of the printer.

If the printer and handheld are moving a lot and changing IP addresses, there are several other things you could do to associate them. You could "register" one of the unique ID's (serial number or MAC address) of the printer or set a friendly name. With some of these, you may have to do a local search for all Zebra devices and query each one till you find the right one. It depends on the parameter you save and the library you are using to find the printer.